Pattern Dystrophy

Patients with this condition present with yellow, vitelliform lesions in the macula with reticular hyperpigmentation. Key differentiating features include younger patients with pattern dystrophy and the FA findings. FA shows early hypopigmentation and surrounding hyperpigmentation with late staining of vitelliform areas [51–54].

Old Exudative AMD

CNV that has either been treated or involutes can leave atrophic changes. Old subretinal or subRPE tissue as seen on clinical exam or on OCT may help to differentiate old CNV from geographic atrophy.

Old Laser Scars

The history of prior laser treatment should be obtainable in these cases. In addition, FA should reveal areas of hypofluorescence that correspond to the laser scars, as opposed to areas of atrophy in AMD that usually are hyperfluorescent.

Other Conditions

Some other conditions that may mimic drusen or dry AMD include:

Hard exudates Cotton wool spots

Type II membranoproliferative glomerulonephritis [55]

Exudative AMD

Central Serous Chorioretinopathy

Patients with CSCR may have serous retinal detachments or sub-RPE fluid (RPE detachment) and can be mistaken for RPE detachments in wet AMD. Differentiating factors include age (usually ages 25–50), lack of drusen, absence of hemorrhage, and multiple areas of hyper and hypoflourescence on ICGA. The natural history is significantly different with visual recovery being common in CSR [42–46].

Idiopathic Polypoidal Choroidal Vasculopathy

Patients with IPCV are typically elderly and suffer from hypertension just as in wet AMD. Differentiating factors include darkly pigmented individuals, lack of drusen, multiple serosanginous RPE detachments with a significant lipid component (rare variant of neovascular AMD, as well), minimal fibrous component (rare disciform scar formation), red-orange color of complex (as opposed to grey-green), and choroidal vascular channels terminating in polyp-like structures on ICGA [28–31].

Retinal Angiomatous Proliferation (RAP)

Retinal angiomatous proliferation is often difficult to be fully differentiated from exudative AMD especially in stage 3 and is largely considered a

subset of AMD. Typical features include retinal hemorrhages, prominent cystoid macula edema, elderly (85 years), and Caucasian. ICGA can detect hot spots (Fig. 3.13) [25–27].

Presumed Ocular Histoplasmosis Syndrome (POHS)

Patients with POHS have punched out yellowwhite chorioretinal scars in the midperiphery, chorioretinal scarring adjacent to optic nerve/ peripapillary atrophy, and CNV. It is more common in the Ohio-Missippi River Valley and in younger individuals (20–50) (Fig. 3.14) [10].

Angioid Streaks

Angioid streaks are bilateral reddish-brown subretinal bands radiating from the optic disc representing calcified Bruch’s membrane. About 50% of the time, an associated condition such as Ehlers– Danlos, pseudoxanthoma elasticum, Padget’s

Fig. 3.14 A patient with presumed ocular histoplasmosis syndrome with punched out chorioretinal lesions, peripapillary atrophy, and CNV

disease, and sickle cell disease can be found. Key differentiating features are the peripapillary streaks, which show as window defects on FA due to overlying atrophy (Fig. 3.15) [56, 57].

High Myopia

Patients with myopic degeneration may develop macular CNV. The key differentiating feature of this condition is the history of significant myopia (at least 6 diopters). Other features include lack of drusen, lacquer cracks (yellow subretinal streaks), macular hyperpigmented spots representing nonprogressing CNV (Fuchs spot), and optic nerve anomalies including an oblique insertion (tilted) of the optic nerve and an area of white sclera and/or choroidal vessels (myopic crescent) surrounding the nerve (Fig. 3.16) [47, 48].

Cystoid Macular Edema

Patients with neovascular AMD may develop CME. However, some patients diagnosed with cystoid macular edema have undiagnosed occult CNV lesions. This is specifically relevant in patients with the diagnosis of idiopathic CME or post-cataract surgery CME. FA is particularly useful in these patients.

Pearl

Rule out occult CNV in cases of CME of unknown etiology or CME in the postoperative setting.

Fig. 3.16 Fundus photo of old CNV due to myopic degeneration

Traumatic Choroidal Rupture

Acutely there is often subretinal hemorrhage in or adjacent to the rupture and CNV can later form on the edge of the rupture site. These patients typically have unilateral findings and a history of significant trauma.

Macular Hemorrhage

Hemorrhage secondary to retinal arterial macroaneurysm, valsalva retinopathy, and trauma can be confused with hemorrhage from AMD. Differentiating features include lack of associated AMD findings, history, and unilateral findings.